Process of making pressure sensitive record material



patented Apr. 25, 1959 PROCESS OF MAKING PRESSURE SENSITIVE RECORDMATERIAL Barrett K. Green, Dayton, Ohio, assignor to The National CashRegister Company,

Dayton,

Ohio, a corporation of Maryland No Drawing. Original applicationNovember 8,

1947, Serial No. 784,939. Divided and this application December 2, 1948,Serial No. 63,211

11 Claims.

This invention relates to improvements in process making apressure-sensitive record material. This application is a division ofthe pending application of Barrett K. Green, Serial No. 784,939, filedNovember 8, 1947, for Process of making pressure-sensitive recordmaterial.

The principal object of this invention is to provide a process of makinga pressure-sensitive record material, on which a mark of distinctivecolor may be produced. by the mere application of localized pressure,and which is not subject to the disadvantages inherent in thepressuresensitive record material disclosed in United States LettersPatent No. 2,299,693, patented October 20, 1942, on the applicationfiled by Barrett Green on February 23, 1940. That patent discloses apressure-sensitive record material including the combination of aninsulating medium, a rupturable solid material such as gum dammar,having included therein interspersed droplets of a plurality of liquidreagents, which are chemically reactive to produce a distinctive colorin the record material :at the points of application of localizedpressure thereto, such pressure rup=- turing the insulating medium topermit chemical reaction between the two liquid reagents. The tworeagents disclosed in this patent are gallic acid and rric ammoniumsulphate, each dissolved in glycerine. These reagents are ionized by theglycerine, which constitutes an ionizing medium, and the chemicalreaction proceeds by interchange of ions when the two solutions areallowed. to mix, upon the rupture of the insulating medium. The reactiondisclosed in that patent depends upon the presence of the reagents in anionizing medium. However, any available ionizing medium is hygroscopic,with the result that the record material, made in accordance with thispatent, is sensitive to an excess of moisture, and conditions of highhumidity may cause the insulating medium to cease to be effective, withthe result that the chemical reaction takes place without anyapplication of localized pressure, and the record material is stainedand discolored, so that it ceases to be useful.

As stated above, the principal object of the present invention is toprovide a process of making a pressure-sensitive record material that isnot subject to the defects and disadvantages of that disclosed in PatentNo. 2,299,693, as indicated above.

Another object of the present invention is to provide a process ofmaking a record material upon which a mark of distinctive color may beproduced, at the points of application of localized pressure thereto, bysuch mere application of localized pressure, and which will not becomediscolored or stained due to the effect of light, atmosphericconditions, or aging.

In short, it is the object of this invention to provide a process ofmaking a pressure-sensitive record material in which the mark ofdistinctive color will be produced only at the points of application oflocalized pressure, and at no other points, and under no otherconditions.

Another object of this invention is to provide a process of making apressure-sensitive record material in which the mark of distinctivecolor is produced by the chemical reaction of colorforming reactants, inthe absence of any liquid ionizing medium therefor.

A further object of this invention is to provide a process of making apressure-sensitive record material in which a mark of distinctive coloris produced by a reaction between solid particles of color-formingreactants.

Further objects, and objects relating to details and economies ofoperation, will definitely appear from the detailed description tofollow. The objects of this invention have been attained by the severalembodiments thereof described in detail in the following specification.This invention is clearly defined and pointed out in the appendedclaims.

In general, the present invention contemplates a process of making apressure-sensitive record material including the forming on a supportingmember a film-like deposit of solid particles of a plurality ofadsorption color-forming reactants disposed in contiguity with eachother, such reactants being so selected that they react, in the absenceof a liquid ionizing medium for the reactants, to form a distinctivecolor when brought into contact with each other, and a solid insulatingmedium insulating said reactants from colorforming reaction contact witheach other. Upon application of localized pressure to the recordmaterial, as by drawing a stylus across it, the insulating medium isruptured at the points of application of said localized pressure, andsuch rupture permits color-forming reaction contact between thereactants at such points, in the absence of any liquid ionizing mediumfor said reactants. The result is that a mark of distinctive color isproduced by the mere application of localized pressure.

The color reaction employed is of the, so-called, adsorption typewherein an inorganic compound causes a color change in an organiccompound coming into adsorption contact therewith.

Of the reactant materials employed the organic material is an electrondonor aromatic compound having a double bond system which is convertibleto a more highly polarized conjugated form upon taking part in anelectron acceptor-donor solid surface chemical reaction, giving itadistinctive color, and the inorganic material is a material which is anacid relative to the organic material so as to be an electron acceptorwhen in adsorption contact therewith. Both materials are in fineparticle form in order to furnish a large reactant surface area per unitarea of the record material which enhances the depth of color per unitarea of the record material.

According to one embodiment of the invention, solid particles of aplurality of color-forming reactants are interspersed in a solidinsulating medium, which insulates the particles from colorformingreaction contact with each other. The rupture of this solid insulatingmedium by the application of localized pressure permits the solidparticles of color-forming reactants to react with each other, at thepoints of application of such pressure, to produce the mark ofdistinctive color. meaning to another form of this invention, solidparticles. of one of thecolor-forming reactants are carried by anddispersed in a solid insulating-medium, to which a coating of solidparticles of another color-forming reactant is applied. In this caseftheapplication of localized pressure ruptulresjthe solid insulating medium,at the pointsof application of such pressure, and brings aboutcolor-forming reaction contact between thei solid particles ofcolor-forming reactants at suchpoints, thus producingthe mark ofdistinctive -co1or. Preferably, this pressure-sensitive recordmaterialincludes a base web, such as a fibrous web. of paper or the like, towhich the coatingof fsolid insulating medium and the colorformingreactants is applied.

The insulating medium is a pressure-rupturable filrnderiveol from anorganic film-forming hydrophilic colloid substance.

Since it is difficult to show precisely the spatial relationship betweenthe solid particles of colorfor fning reactants, the solid insulatingmedium, an d the base web, it is preferred not to attempt to illustrateany embodiment of this invention by drawings.

Inithe following examples, there will be describedembodiments of thisinvention, by means offwhich-the objects of the invention have beensuccessfully attained.

' One embodiment of this invention produces a material comprising a baseweb of paper or the likiebhavin g applied thereto a coating includingcasein ,or methyl cellulose as the solid insulating medium and solidparticles of two color-forming rea ctantsj namely, kaolin and thecompound 3,3; bis(p-dimethylaminophenyl) phthalide, alsoknownas'Pmalachite green lactone, having the structure This recordmaterial is normally white or light in color, and, upon application oflocalized pressure'th er eto, as by drawing a stylus thereover, a markof dark'blue-green color is produced at the points of application ofsuch pressure. The solid insulating medium in this record materialserves to insulate the solid particles of kaolin and malachite greenlactone from color-forming reaction contact with each other, and thisinsulating medium is ruptured, at the points of application of localizedpressure, to permit such colorformin reaction contact, resulting in themark of distinctive color. This pressure-sensitive record material isnot affected substantially by atmospheric moisture and remains stableover long periods of time. According to this embodiment of theinvention, the solid insulating medium may be casein or methylcellulose, but other organic film-forming hydrophilic colloid materialssuch as gelatin, starch, polyvinyl alcohol or animal glue may be usedinstead. Attapulgite (Attapulgus clay), pyrophyllite, talc, bentonite,halloysite, calcium sulphate, magnesium trisilicate, zinc sulphide, andcalcium fluoride are inorganic materials, any one of which may besubstituted for the kaolin as one of the color-forming reactants. Whenany of these materials are substituted for the kaolin, the resultingrecord material will be white or light in color, and a dark blue-greenmark will appear thereon as the re sult of the application'of localizedpressure.

Another embodiment of the invention for making the record materialdescribed above consists of the following method: A slurry of kaolin andwater was prepared including fifty parts by weight of kaolin to fiftyparts by weight of water, and a minor proportion, such as 0.3% byweight, of a suitable dispersing agent, such as sodium metaphosphate,was added to facilitate the dispersion of the particles of kaolinthrough the slurry and to reduce its viscosity. A 20% by weight solutionof casein in water was formed by, first, disper ing the casein in coldwater by stirring for fifteen minutes at room temperature, and, thenheating up to 60 degrees centigrade. Five parts of a 28% ammoniumhydroxide solution were then added to the hot casein solution, which wasstirred for about fifteen minutes and allowed to cool to roomtemperature. The kaolin slurry and the alkaline caseinsolution were thenthoroughly mixed in the ratio by Weight of kaolin to casein of 10 to 1,and blended, and it was found desirable to add a small percentage oftributyl phosphate in alcohol, or other antifoaming agent, at thisstage. This mixture of the kaolin slurry and the casein solution wasthen applied as a coating to the paper, dried thereon, and then calndered or treated in any desired way to give the proper surface finish.A solution in toluene of about 3% by weight of malachite green lactonewas then applied to the coated side of the paper. The excess of thissolution was removed and the treated paper dried to evaporatethe'toluene, after which it was ready for use.

According to another embodiment of the invention, the pressure-sensitiverecord material described above, having methyl cellulose as the solidinsulating medium and kaolin and malachite green lactone as thecolor-forming reactants, was successfully made by the following method:A solution was prepared by dissolving about 5 parts by weight of methylcellulose in about 50 parts by weight of Water, which solution wasdivided into two equal parts" To one portion of this methyl cellulosesolution, the slurry of kaolin and water prepared as described above wasadded, in the ratio by weight of kaolin to methyl cellulose of 40 to 1,and thoroughly *7 mixed. The other portion of themethyl-cellulosesolution was rendered alkaline by, the addi. tion of ammonium hydroxidesolution, to an eX- tent sufficient to precipitate the malachite greenlactone from the acid solution thereof mixed with this portion. 6 gramsof malachite green lactone were dissolved in 50 cc. of 3.7% hydrochloricacid solution, and this acid solution was mixed with the ammoniacalportion of the methyl cellulose solution, in such proportions that theratio by weight of kaolin to malachite green lactone in the coating willbe about 100 to 3, the mixture being neutral or slightly alkaline, sothat the malachite green lactone is precipitated therein. The twoportions of the methyl cellulose solution were then thoroughly mixed andapplied as a coating to the paper, which coating was dried in the usualmanner.

When these ingredients, in either embodiment, are applied to the paperas a coating thereon, such coating should weigh about .0023 pound persquare foot or" surface and should have a thickness of the order of from.0005 to .001 inch. The thickness of the coating varies, of course, withthe treatment to which to record material is subjected in finishing. Thesolid particles of kaolin in this record material may be of about theorder of ten microns in diameter, although considerable variation inparticle size is possible without any ill effects. Particle size of themalachite green lactone is largely determined by the method ofapplication of that ingredient. The particles of the reactant may be aslarge as ten microns in diameter and frequently are much smaller.

The pressure-sensitive record materials disclosed herein are not claimedin this application but are disclosed and claimed in the pendingapplication of Barrett K. Green, Serial No. 784,938, filed November 8,1947, for Pressuresensitive record material, and in a division thereof,Serial No. 59,422 filed November 10, 1948.

It is understood that the process of making a pressure-sensitive recordmaterial described herein is susceptible of considerable variationwithout departing from the spirit of the invention.

What is claimed is:

l. The process of making a pressure-sensitive record material includingthe forming on a supporting member a film-like deposit of solidparticles of a plurality of adsorption color-forming reactants disposedin contiguity with each other and a solid insulating medium, derivedfrom an organic film-forming hydrophilic colloid substance, insulatingsaid reactant particles from color-forming reaction with each other, atleast one of said reactants being an inorganic compound and at leastanother of said reactants being an organic compound adsorbabletherewith, said reactants being so selected as to react, in the absenceof a liquid ionizing medium for the reactants, to form a distinctivecolor when brought into contact with each other, one of saidcolorforming reactants being the compound 3,3 bis(pdimethylaminophenyl)phthalide, having the structure and the inorganic reactant being in fineparticle form providing a large adsorbent surface area and which is anacid relative to the organic reactant so as to be an electron acceptorwhen in adsorption contact with said organic reactant.

2. The process of making a pressure-sensitive record material includingthe steps of coating a supporting member with a film of solid insulatingmaterial, derived from an organic film-forming hydrophilic colloidsubstance, having particles of a first color-forming solid reactantdispersed therein, and depositing on said film particles of a secondcolor-forming solid reactant, one of said reactants being an inorganiccompound and the other of said reactants being an organic compoundadsorbable with it and said reactants being so selected as to form adistinctive color when brought into contact with each other, and saidsolid insulating material being such as to insulate the reactants fromcolor-forming reaction contact with each other, the second color-formingreactant being the compound 3,3 bis(p-dimethylaminophenyl) phthalide,having the structure and the inorganic reactant being in fine particleform providing a large adsorbent surface area and which is an acidrelative to the second reactant so as to be an electron acceptor when inadsorption contact with said second reactant.

3. The process of making a pressure-sensitive record material includingthe step of forming on a supporting member a film of a solid insulatingmedium, derived from a film-forming hydrophilic colloid substance,having interspersed therein solid particles of a plurality of colorforming reactants, disposed in contiguity but insulated fromcolor-forming reaction contact by such medium, at least one of thereactants being an inorganic compound and at least another of thereactants being an organic compound adsorbable with it, said reactantsbeing so selected as to react in the absence of an ionizing medium toform a distinctive color when brought into contact with each other, oneof the color-forming reactants being the compound 3,3 bis(p-dimethylaminophenyl) phthalide, having the structure and theinorganic reactant being in fine particle form providing a largeadsorbent surface area and which is an acid relative to the organicreactant so as to be an electron acceptor when in adsorption contactwith said organic reactant.

4. The process of claim 3 in which the inorganic color-forming reactantsis kaolin.

5. The process of claim 4 in which the solid insulating medium is methylcellulose.

6. The process of making a pressure-sensitive iatoeg iei record materialincluding the steps of forming a dispersion of solid particles of afirst-color-forming reactant in a solution of a solid insulating mediumderived from an organic film-forming hydrophilic colloid substance,forming a dispel sion of solid particles of a secondcolor-formingreactant in a solution of said insulating medium, mixing saiddispersions, coating a base web with the mixture of said dispersions,and evaporating the solvent therefrom, leaving on the base web Iacoating of solid-insulating mediumhaving said solidreactant-particlesinterspersed therein, one of said reactants being an inorganic compoundand the other of said reactants being an organic compound adsorbablewith'it and said reactants being so selecte'd as to' react in theabsence of an ionizing medium-to form a distinctive color when broughtinto adsorption contact with each other, the second color-formingreactant being the compound 33 bis (p-dimethylaminophenyl)' phthalide,having the structure 113) :N' N 0 H) 2 and the inorganic reactant beingin fine particle form providing a large adsorbent surface area and whichis an acid relative to the organic reactant so as'to be ail-electronacceptor when in adsorption contact with saidorganic reactant.

'7. The process of claim 6 in which the inorganic color-forming reactantis kaolin.

8. The process'of claim 7 in which the" solid insulating medium ismethyl cellulose.

9. The processof making a pressure-sensitive record material includingthe steps of forming a dispersion of solid particles of a firstcolor-form ing reactant in a solution of a solid insulating mediumderived from an organic film-forming hydrophilic' colloid substance,forming a dispersion of solid particles of a secondcolOr-forming 8reactantin a solution of saidlinsulating medium; mixing saiddispersions, coating a base web with the mixture of said dispersions andevaporating the solvent therefrom, leaving on the base web a coating ofsolid insulating medium having said solid reactant particlesinterspersed therein, one of' said reactants being an inorganic compoundand the other of said reactants being an organic compound adsorbablewith it and said reactants being so selected as to react in the absenceof an ionizing medium to form a distinctive color when brought intoadsorption contact with each other, the dispersion of the solidparticles of the second color-forming reactant being formed byprecipitation thereof by the neutralization of an acidified solution ofsaid reactant in the insulating medium, said particles being made of thecompound 3,3 bis(p-dimethylaminophenyl) 6-di methylamino phthalide,having the structure REFERENCES CITED The followingreferences are ofrecord in the file of this patent:

FOREIGN PATENTS Country Date Great Britain Jan. 4, 1943 Number

1. THE PROCESS OF MAKING A PRESSURE-SENSITIVE RECORD MATERIAL INCLUDINGTHE FORMING ON A SUPPORTING MEMBER A FILM-LIKE DEPOSIT OF SOLIDPARTICLES OF A PLURALITY OF ADSORPTION COLOR-FORMING REACTANTS DISPOSEDIN CONTIGUITY WITH EACH OTHER AND A SOLID INSULATING MEDIUM, DERIVEDFROM AN ORGANIC FILM-FORMING HYDROPHILIC COLLOID SUBSTANCE, INSULATINGSAID REACTANT PARTICLES FROM COLOR-FORMING REACTION WITH EACH OTHER, ATLEAST ONE OF SAID REACTANTS BEING AN INORGANIC COMPOUND AND AT LEASTANOTHER OF SAID REACTANTS BEING AN ORGANIC COMPOUND ADSORBABLETHEREWITH, SAID REACTANTS BEING SO SELECTED AS TO REACT, IN THE ABSENCEOF A LIQUID IONIZING MEDIUM FOR THE REACTANTS, TO FORM A DISTINCTIVECOLOR WHEN BROUGHT INTO CONTACT WITH EACH OTHER, ONE OF SAIDCOLORFORMING REACTANTS BEING THE COMPOUND 3,3 BIS(PDIMETHYLAMINOPHENYL)PHTHALIDE, HAVING THE STRUCTURE